As a built-up type toy, there are a type that can be assembled and disassembled easily without any adhesive such as a piling-up type toy or an assemblage type toy, and a type that cannot be disassembled after being assemble using adhesive such as a plastic model.
Furthermore, among the former type of built-up type toy that does not use the adhesive, there has been developed a toy that a character, a symbol, a diagram or any other kinds of shape is configured by assembling the respective parts so as to be used for the education of the infant.
However, the built-up type toy that does not use the adhesive has the problems that the assembled shape can be easily demolished even by a slight impact to the assembled shape as the joint of the parts is not steadfast, and if the mechanical joining structure is adopted to prevent such a shortcoming, the lifetime of the product becomes short by the repetitive assembling and disassembling.
In particular, in the case of the built-up type toy provided for the purpose of education of the infant as described above, considering the aspect that it is handled by the infant who is not delicate in the hand movement and not careful sufficiently, the fact that it is not easy to assemble and the assembled shape can be demolished easily has been a serious problem to be solved for a long period of time in the infant toy industry.
Furthermore, in the case of the structure that employs the assembling fashion to pile up a various shape of parts such as Lego, the assembled structure can be realized under the restriction that the center of weight is kept as there is not provided a separate joining structure on the joining surface of the parts, which has been another problem that the toy useful for the education to develop the initiative of the infant cannot be provided.